User manual JBL W15GTI

[. . . ] Power-Handling Limitations The power-handling capacity of any subwoofer is related to the excursion limit of its suspension and its ability to dissipate heat. A speaker reaches its excursion-limited power-handling capacity when its suspension is stretched to its limit. The excursion curve shown on the Enclosure Design Sheet (included with your woofer) displays cone excursion at the input power level required to drive the woofer to maximum linear excursion (Xmax). Thermal power handling is determined by the amount of heat that may be dissipated by the driver's voice coil. [. . . ] If you wish to use a vented enclosure, we strongly recommend having your authorized JBL dealer build it; or verify that your design is correct if you wish to build it yourself. An optimum vented enclosure is always larger than the optimum sealed box for the same woofer, and will require more space inside the vehicle. TM Bandpass enclosures can provide the greatest output available from any amplifier and subwoofer combination ­ at the expense of sonic accuracy. If sheer SPL (sound pressure level) is what you desire most, choose a vented or bandpass enclosure. Bandpass enclosure design is very tricky and the aid of a computer and enclosure design software is necessary if you wish to design the enclosure yourself. Like a vented enclosure, a bandpass enclosure must be built exactly to the specifications provided. Bandpass enclosures can be quite large and may require a lot of space inside your vehicle. 03 The Official Brand of Live Music Enclosure Construction Please observe the following suggestions when building an enclosure for GTi Series subwoofers. Choose an enclosure design from the Enclosure Design Sheet included with your subwoofer. Use at least 3/4" (19mm) MDF (medium density fiberboard) or marine birch plywood to build the enclosure. Enclosures for 12" and larger subwoofers and smaller woofers driven by high-power amplifiers should be constructed using 1" (25mm) material. Once the box has been tested, seal all joints inside the box with silicone caulk. Fill the enclosure with damping material (dacron, fiberglass insulation or long-fiber wool) according to the design you have chosen from the Enclosure Design Sheet. "0% fill" indicates that no damping material should be used; "50% fill" indicates that all interior walls except the baffle should be lined with 1" thick damping material, and "100% fill" indicates that the box should be loosely stuffed with damping material. Keep in mind that the openings at either end of the port must be at least one port diameter away from any obstruction. Use the 10/24" machine screws and T-nuts provided to mount the woofer to the baffle. Dual Coil Versus Differential Drive® (patent pending) Conventional dual-voice-coil woofers use a pair of voice coils "interwound" on the former and centered in the magnetic gap. The two coils may be connected in series or parallel in order to maximize an amplifier's output power. Xmax (one-way-linear) is determined by the amount of voice coil exposed above and below the top plate. A conventional voice coil is made up of several layers of windings, each transferring heat to the winding next to it until the heat is finally dissipated by the outside layer through the top plate, magnet and backplate. This arrangement is inefficient, and results in low thermal power handling. Conventional dual-voice-coil design CONE BOTH COILS DRIVE CONE FORWARD AND REARWARD SPIDER OVERHANG DETERMINES Xmax TOP PLATE MAGNET POLE PIECE / BACKPLATE Figure 1. [. . . ] Connecting the voice coils in parallel (3 ohms) Note: Connect the coils in parallel if you are connecting a single woofer to an amplifier. TERMINAL JUMPER INTACT RED TERMINAL TERMINAL JUMPER INTACT BLACK TERMINAL + Figure 6. Connecting the voice coils in series (12 ohms) CONE TOP COIL IN GAP #1 DRIVES CONE FORWARD GAP #1 SPIDER TERMINAL JUMPER REMOVED RED TERMINAL TERMINAL JUMPER REMOVED 1st TOP PLATE MAGNET BLACK TERMINAL POLEPIECE OVERHANG DETERMINES Xmax GAP #2 2nd TOP PLATE + BOTTOM COIL IN GAP #2 DRIVES CONE REARWARD ALUMINUM COVER 05 The Official Brand of Live Music Configuring multiple woofers for connection to a single amplifier: Figure 7. Connect two woofers in parallel (with coils in parallel) for a 1. 5-ohm load Figure 8. Connect three woofers in parallel (with coils in series) for a 4-ohm load Figure 9. [. . . ]